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Abstract: A new superionic conducting transparent phosphate glasses with composition Li(4+x)Ti x Nb1−x P3O12 (0 ≤ x ≤ 1.0) were prepared by rapid melt quenching. As quenched samples were characterized by X-ray powder diffraction, differential scanning calorimetric and Fourier transform infrared spectroscopy studies. These glasses were found to have high thermal stability parameter and Li4NbP3O12 has been found to have high glass forming ability. Electrical properties of the present glasses were studied by impedance and dielectric spectroscopy in the frequency range 10 Hz–3 MHz in the temperature range 323–523 K. Arrhenius behavior has been observed for all the glass in conductivity, dielectric loss and conductivity relaxation and their activation energies are explained and reported. [Copyright &y& Elsevier]

Abstract: Niobium based glasses of composition Na2NbMP3O12 (where M=Cd, Zn, Pb and Cu) have been synthesized by melt quenching method and characterized by XRD, FTIR and DSC. The ac conductivity measurements have been carried out over wide range of frequencies at different temperatures on these glassy systems. Ac conductivity data are analyzed using conductivity and electric modulus formalisms. The bulk dc conductivity obtained from complex impedance plots follow the Arrhenius behavior and its activation energy matches well with the activation energy obtained from electric modulus formalism. The ac conductivity plot exhibits universal power law features and the temperature dependence of dc and ac conductivity is discussed. The scaling behavior of the ac conductivity and electric modulus spectra with respect to temperature are discussed and reported for these glassy systems. [Copyright &y& Elsevier]

• Nanocrystalline α-Fe 2 O 3 shows a dielectric loss peak at higher frequencies. • Combined Cole-Cole conduction and dielectric relaxation function is used to study the electrical properties of the material. • The material possesses pinned and free dipoles. • Hopping of charge carriers and lattice disorder create a combined relaxation in the material. The present study elucidates the temperature and frequency-dependent electrical properties of α-Fe 2 O 3 synthesised by co-precipitation method. XRD and Raman spectroscopy are employed to study the formation and crystal structure of the material. The material shows two relaxation peaks in the frequency range 1 Hz–1 MHz. The ac electrical data of the material are analysed with the novel relaxation function combining conduction and dielectric relaxations. The results reveal that the material possesses two types of dipoles, one corresponds to the free dipoles of FeO 6 molecules, and the other corresponds to the pinned dipoles created by charge carriers and ion lattice. The dc conductivity, conduction relaxation time and dielectric relaxation time obey Arrhenius law. [ABSTRACT FROM AUTHOR]

Most of the crystalline materials seldom show a well-defined dielectric loss peak due to domination of dc conductivity contribution, but effects of loss peaks are seen at high frequencies. Ac electrical data of nano-crystalline Mn 0.5 Zn 0.5 Fe 2 O 4 synthesised by chemical co-precipitation method show such behaviour. Properly combined and formulated conduction and dielectric relaxation functions are required for such materials. Cole–Cole type relaxation function in the combined conduction and dielectric process is formulated for complex resistivity ρ ⁎ ( ω ) , complex permittivity ε ⁎ ( ω ) , complex conductivity σ ⁎ ( ω ) and complex electric modulus M ⁎ ( ω ) . Conduction and dielectric relaxation are linked to Jonscher's idea of ‘pinned dipole’ and ‘free dipole’ to understand the relaxation dynamics. The physical parameters of ‘pinned dipole’ and ‘free dipole’ formalism are unique for all representations like ρ ⁎ ( ω ) , ε ⁎ ( ω ) , σ ⁎ ( ω ) and M ⁎ ( ω ) . ‘Pinned dipole’ relaxation time τ c related to conduction process and ‘free dipole’ relaxation time τ d related to dielectric process show Arrhenius behaviour with the same activation energy. Correlation of dc conductivity σ c with τ c and τ d indicates the coupled dynamics of ‘pinned dipole’ and ‘free dipole’. Time–temperature scaling of conduction and dielectric relaxation reveals that the mechanism of coupled dynamics of ‘pinned dipole’ and ‘free dipole’ is temperature independent. Hopping of charge carriers with dynamics of disordered cation distribution of host matrix generates a coupled conduction and dielectric relaxation in Mn 0.5 Zn 0.5 Fe 2 O 4 . [ABSTRACT FROM AUTHOR]